Is this typical for room gain? (1 Viewer)

[Dan_M]

I have a +20db hump that peaks at 45hz. I'd post a graph but apparently I'm not allowed to yet.

18hz : 75db
32hz : 85db
45hz : 95db
68hz : 85db
80hz : 75db

The graph is more or less a symmetrical hump with a few small peaks at the begining and end. Is a BFD my only option besides finding a better spot for it?

 

[Craig Chase]

Do you happen to have a fairly square room with roughly 12-13 foot dimensions ?

 

[Dan_M]

The entire room is about 17'x22', 9 of the 22 feet is a kitchen seperated only by a small half-wall bar thing about 7' long. Right now I have the couch sorta in the middle of the room with the sub behind it in the corner. I was thinking about centering the sub on the wall behind the couch to get it out of the corner. Having the sub up front with the mains isn't really an option since that wall is shared by neighbors and I'd like to keep the sub as far from this wall as possible.

 

[Craig Chase]

Dan - What subwoofer do you have?

 

[Dan_M]

It's a ported 142.5l DIY tuned to 18.1hz, 12" Dayton Titanic MK3 powered by a 250W amp.

 

[Craig Chase]

Thanks... You are seeing about a 8-10 dB peak... Even though the sub is tuned to 18 Hz... I have a Denali tuned to 18.5 Hz,and the 18 Hz level is 12 dB below the 32 Hz level...

You want to get the sub as flat as possible through experimenting with placement... then add EQ... either BFD or another... and boost the 18 to 28 Hz range, and drop the 36-44....

 

[Michael R Price]

That peak would be nearly ideal to equalize out (you'd get more headroom too). Or you could try setting a crossover near 45Hz and adjust the subwoofer phase to cancel your main speakers. That would probably do the trick, but it's risky in terms of compromising upper bass performance, since the lowpass crossover in the plate amps is not very steep.

 

[Dan_M]

I tried playing with the crossover and moving it out of the corner with no luck. Do you guys think it'd be worth it to worry about this hump and EQ it? Does a flat sub really sound the best? The biggest potential advantage I can think of is for music,it may tighten up the bass a bit.

 

[Lee Carbray]

Care to explain how he would gain more headroom by EQ'ing?

 

[Michael R Price]

Well, the sub would have less information in the 45Hz range to deal with, so it could play louder at the other frequencies.

 

[Lee Carbray]

Right. But they wont just play louder on their own. He will have to up the gain to keep the overall response even. Which would cause him to lose headroom. Or am I crazy? I have always read EQ reduced headroom. I know it did when I reduced the 50Hz peak with my BFD. I guess if he did not recalibrate after the EQ then there would be more headroom.

 

[Lee Carbray]

Right. But they wont just play louder on their own. He will have to up the gain to keep the overall response even. Which would cause him to lose headroom. Or am I crazy? I have always read EQ reduced headroom. I know it did when I reduced the 50Hz peak with my BFD. I guess if he did not recalibrate after the EQ then there would be more headroom.

 

[Dan_M]

Would it be better to EQ everything down to 75db, instead of adding gain at the front and end of the hump to bring it up to 85db? I can see gaining a bit of headroom if I lowered everything to 75db. I have plenty of room to add overall gain to the incoming signal if I need to, the LFE is set at -18db at the reciever.

 

[Dan_M]

Would it be better to EQ everything down to 75db, instead of adding gain at the front and end of the hump to bring it up to 85db? I can see gaining a bit of headroom if I lowered everything to 75db. I have plenty of room to add overall gain to the incoming signal if I need to, the LFE is set at -18db at the reciever.

 

[Lee Carbray]

It is definetly better to cut then to boost. You may find though that you will need to increase the volume once you have made the cut because overall it sounds lower.

I must mention as well becasue nobody else has that another option besides a BFD is acoutical treaments like bass traps and such.

Also just to make sure you used 1/6th octave tones, and not just the ones above right? If you want to send me the graph I can host it for you.

 

[Lee Carbray]

It is definetly better to cut then to boost. You may find though that you will need to increase the volume once you have made the cut because overall it sounds lower.

I must mention as well becasue nobody else has that another option besides a BFD is acoutical treaments like bass traps and such.

Also just to make sure you used 1/6th octave tones, and not just the ones above right? If you want to send me the graph I can host it for you.

 

[Michael R Price]

Dan, it doesn't matter. Just try to get a flat (or appropriately contoured) response from the subwoofer and then calibrate it to balance the overall bass level with the rest of the system. Your absolute output capability doesn't really change.

Lee, what you say is true. The sub can produce a certain level of sound at any given frequency and when you EQ it, that doesn't change, but the level of those sounds relative to the other sounds does. A simple way of looking at it is: If your system has a limited bass output, and you reduce the level of the bass relative to everything else, then the overall level you can play to is increased (before the bass starts distorting). Dan's system probably will not gain much from cutting the 45Hz band because the rest of the bass, including the particularly stressful lower frequencies, will probably be brought up in level to maintain a reasonable tone.

 

[Michael R Price]

Dan, it doesn't matter. Just try to get a flat (or appropriately contoured) response from the subwoofer and then calibrate it to balance the overall bass level with the rest of the system. Your absolute output capability doesn't really change.

Lee, what you say is true. The sub can produce a certain level of sound at any given frequency and when you EQ it, that doesn't change, but the level of those sounds relative to the other sounds does. A simple way of looking at it is: If your system has a limited bass output, and you reduce the level of the bass relative to everything else, then the overall level you can play to is increased (before the bass starts distorting). Dan's system probably will not gain much from cutting the 45Hz band because the rest of the bass, including the particularly stressful lower frequencies, will probably be brought up in level to maintain a reasonable tone.

 

[RichardHOS]

I know conventional wisdom says to cut instead of boost, but in your case it doesn't matter. Most people say cut a peak, and don't try to boost a null because it is like a black hole for power. There is some sense in that, though nulls can be boosted moderately with EQ in most rooms.

In your case, at least with the crude measurements you've posted, it won't matter whether you cut the hump and then raise volume to get the average back up, or boost on either side of the hump and then cut the volume to get the average back down. They are equivalent. The only thing to watch for is keeping gains in check through the signal chain to prevent signal clipping, whether in the EQ or otherwise.

 

[RichardHOS]

I know conventional wisdom says to cut instead of boost, but in your case it doesn't matter. Most people say cut a peak, and don't try to boost a null because it is like a black hole for power. There is some sense in that, though nulls can be boosted moderately with EQ in most rooms.

In your case, at least with the crude measurements you've posted, it won't matter whether you cut the hump and then raise volume to get the average back up, or boost on either side of the hump and then cut the volume to get the average back down. They are equivalent. The only thing to watch for is keeping gains in check through the signal chain to prevent signal clipping, whether in the EQ or otherwise.